diff --git a/tests/roots/test-add_source_parser-conflicts-with-users-setting/conf.py b/tests/roots/test-add_source_parser-conflicts-with-users-setting/conf.py
index 3ad549153..5e5790169 100644
--- a/tests/roots/test-add_source_parser-conflicts-with-users-setting/conf.py
+++ b/tests/roots/test-add_source_parser-conflicts-with-users-setting/conf.py
@@ -11,7 +11,10 @@ class DummyTestParser(Parser):
 
 
 extensions = ['source_parser']
-source_suffix = ['.rst', '.test']
+source_suffix = {
+    '.rst': 'restructuredtext',
+    '.test': 'restructuredtext',
+}
 source_parsers = {
     '.test': DummyTestParser
 }
diff --git a/tests/roots/test-add_source_parser/conf.py b/tests/roots/test-add_source_parser/conf.py
index 2acd4d24c..ef85560b8 100644
--- a/tests/roots/test-add_source_parser/conf.py
+++ b/tests/roots/test-add_source_parser/conf.py
@@ -5,4 +5,3 @@ sys.path.insert(0, os.path.abspath('.'))
 
 
 extensions = ['source_parser']
-source_suffix = ['.rst']
diff --git a/tests/roots/test-autosummary/conf.py b/tests/roots/test-autosummary/conf.py
index 46cf4fa1a..f459017f8 100644
--- a/tests/roots/test-autosummary/conf.py
+++ b/tests/roots/test-autosummary/conf.py
@@ -5,8 +5,6 @@ sys.path.insert(0, os.path.abspath('.'))
 
 extensions = ['sphinx.ext.autosummary']
 
-# The suffix of source filenames.
-source_suffix = '.rst'
 autosummary_generate = True
 
 exclude_patterns = ['_build']
diff --git a/tests/roots/test-build-text/conf.py b/tests/roots/test-build-text/conf.py
index fd9eefbf6..b0fdaf8d2 100644
--- a/tests/roots/test-build-text/conf.py
+++ b/tests/roots/test-build-text/conf.py
@@ -1,2 +1,4 @@
-source_suffix = '.txt'
+source_suffix = {
+    '.txt': 'restructuredtext'
+}
 exclude_patterns = ['_build']
diff --git a/tests/roots/test-ext-autodoc/conf.py b/tests/roots/test-ext-autodoc/conf.py
index 979a70983..9d1cdc740 100644
--- a/tests/roots/test-ext-autodoc/conf.py
+++ b/tests/roots/test-ext-autodoc/conf.py
@@ -5,9 +5,6 @@ sys.path.insert(0, os.path.abspath('.'))
 
 extensions = ['sphinx.ext.autodoc']
 
-# The suffix of source filenames.
-source_suffix = '.rst'
-
 autodoc_mock_imports = [
     'dummy'
 ]
diff --git a/tests/roots/test-ext-autosummary/conf.py b/tests/roots/test-ext-autosummary/conf.py
index 55c769c6f..1c0d02202 100644
--- a/tests/roots/test-ext-autosummary/conf.py
+++ b/tests/roots/test-ext-autosummary/conf.py
@@ -5,6 +5,3 @@ sys.path.insert(0, os.path.abspath('.'))
 
 extensions = ['sphinx.ext.autosummary']
 autosummary_generate = True
-
-# The suffix of source filenames.
-source_suffix = '.rst'
diff --git a/tests/roots/test-ext-doctest-skipif/conf.py b/tests/roots/test-ext-doctest-skipif/conf.py
index cd8f3eb11..ae00e3540 100644
--- a/tests/roots/test-ext-doctest-skipif/conf.py
+++ b/tests/roots/test-ext-doctest-skipif/conf.py
@@ -2,7 +2,9 @@ extensions = ['sphinx.ext.doctest']
 
 project = 'test project for the doctest :skipif: directive'
 root_doc = 'skipif'
-source_suffix = '.txt'
+source_suffix = {
+    '.txt': 'restructuredtext'
+}
 exclude_patterns = ['_build']
 
 doctest_global_setup = '''
diff --git a/tests/roots/test-ext-doctest/conf.py b/tests/roots/test-ext-doctest/conf.py
index d0e8b107b..57fc40607 100644
--- a/tests/roots/test-ext-doctest/conf.py
+++ b/tests/roots/test-ext-doctest/conf.py
@@ -2,5 +2,7 @@ extensions = ['sphinx.ext.doctest']
 
 project = 'test project for doctest'
 root_doc = 'doctest'
-source_suffix = '.txt'
+source_suffix = {
+    '.txt': 'restructuredtext'
+}
 exclude_patterns = ['_build']
diff --git a/tests/roots/test-inheritance/conf.py b/tests/roots/test-inheritance/conf.py
index 26cadca50..9953494a5 100644
--- a/tests/roots/test-inheritance/conf.py
+++ b/tests/roots/test-inheritance/conf.py
@@ -4,4 +4,3 @@ import sys
 sys.path.insert(0, os.path.abspath('.'))
 
 extensions = ['sphinx.ext.inheritance_diagram']
-source_suffix = '.rst'
diff --git a/tests/roots/test-intl/conf.py b/tests/roots/test-intl/conf.py
index 96ac664f2..09c47bb06 100644
--- a/tests/roots/test-intl/conf.py
+++ b/tests/roots/test-intl/conf.py
@@ -1,5 +1,7 @@
 project = 'Sphinx intl <Tests>'
-source_suffix = '.txt'
+source_suffix = {
+    '.txt': 'restructuredtext'
+}
 keep_warnings = True
 templates_path = ['_templates']
 html_additional_pages = {'contents': 'contents.html'}
diff --git a/tests/roots/test-templating/conf.py b/tests/roots/test-templating/conf.py
index e03eaf18f..7a2baeda2 100644
--- a/tests/roots/test-templating/conf.py
+++ b/tests/roots/test-templating/conf.py
@@ -1,5 +1,7 @@
 project = 'Sphinx templating <Tests>'
-source_suffix = '.txt'
+source_suffix = {
+    '.txt': 'restructuredtext'
+}
 keep_warnings = True
 templates_path = ['_templates']
 release = version = '2013.120'
diff --git a/tests/roots/test-versioning/conf.py b/tests/roots/test-versioning/conf.py
index 6344cb0dd..d52d1f274 100644
--- a/tests/roots/test-versioning/conf.py
+++ b/tests/roots/test-versioning/conf.py
@@ -1,3 +1,5 @@
 project = 'versioning test root'
-source_suffix = '.txt'
+source_suffix = {
+    '.txt': 'restructuredtext'
+}
 exclude_patterns = ['_build']